Turbo charging is a common means to increase torque and power of an internal combustion engine. Exhaust gas recycling is a common means to improve exhaust gas quality, i.e., to decrease the content of nitrogen oxide in the exhaust gas. When combining external exhaust gas recycling (i.e., guiding some of the exhaust from an exhaust manifold of the engine to an intake manifold of the engine) with turbo charging, it is necessary to increase the pressure of the exhaust recycled to the intake manifold to a pressure level which is at least the same as the pressure level of the pressurized fresh air in the intake manifold.
DE 196 03 591 C1 discloses a turbocharged internal combustion engine with a fresh air turbocharger and an exhaust turbocharger, wherein an exhaust conduit is connected to an inlet of the turbine of the exhaust turbocharger and an inlet of the turbine of the fresh air turbocharger and, in addition, to an inlet of the compressor of the exhaust turbocharger. The outlet of the exhaust turbocharger is connected to a conduit connecting the outlet of a compressor of the fresh air turbocharger to the engine. Upstream of the compressor of the exhaust turbocharger and downstream of the compressor of the fresh air turbocharger are provided coolers. A control valve is connected to the inlets of the compressor and the turbine of the exhaust turbocharger and an exhaust outlet of the engine to control the rate of exhaust recycling.
DE 44 36 732 A1 discloses a turbocharged internal combustion engine with a fresh air turbocharger and an exhaust turbocharger with the inlets of their turbines being connected in parallel to the exhaust side of the engine. The exhaust side of the engine is, in addition, connected via a cooler to an inlet of the compressor of the exhaust turbocharger. The outlet of the compressor of the exhaust turbocharger is connected to an inlet manifold of the combustion engine, which inlet manifold is also connected via a cooler to an outlet of the compressor of the fresh air turbocharger. For the purpose of controlling the exhaust recirculating rate, a control valve is provided upstream of the inlet of the turbine of the exhaust turbocharger.
The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior turbocharged internal combustion engines with exhaust recycling, as, e.g., mounting efforts, complexity and/or efficiency.